We plan to study equine recurrent uveitis to determine the nature of the immune response which leads to tissue damage by investigating clinical cases and also by inducing the disease with Leptospira pomona and Onchocerca cervicalis microfilaria. Indwelling catheters will be placed into the anterior chamber, and sequential sample of aqueous collected and monitored for evidence of cellular and humoral immunity to uveal antigens and to Leptospirae and/or onchocercal antigens. We will use microagglutination and the radioallergosorbent test (RAST) and also lymphocyte blastogenesis and leucocyte migration inhibition. We will aso assay for immune complexes by C1q binding assay. By performing similar studies on blood and quantitating albumin in both serum and aqueous, we will acquire evidence as to the relative role of local and systemic responses. The pathogenicity of local responses will be assessed by innoculating normal eyes. These studies, performed on arguably the best available experimental model for recurrent uveitis of man, should provide insight in to the nature and interaction of the immune mechanisms responsible for the etiopathogenesis of this serious ocular disease. Only then can national therapeutic regimes evolve.